Resistance to zinc sulphate of the zebrafish (Brachydanio rerio Hamilton-Buchanan) at different phases of its life history.

SUMMARY Zebrafish of eleven age groups were exposed to four concentrations of zinc sulphate (5, 10, 20 and 40 p.p.m. Zn) in soft water (CaCO3 10 p.p.m.) at 25d C. In all four concentrations, newly laid eggs generally survived the longest time. Survival time decreased with age until hatching on the fourth day. Newly hatched fish (4–13 days old) survived the shortest time. Forty-day-old fish and adults (100 days old) survived slightly longer in the two highest concentrations. In the two lowest concentrations, 40-day-old fish survived as long as newly laid eggs, and many adults survived indefinitely. The threshold concentration of zinc was approximately 10 p.p.m. for adults and 1.3 p.p.m. for 40-day-old fish.